What is referred to as completion relates to operations of preparation or outfitting necessary for bringing a geologic formation into production from the wellbore. These completion operations utilize particular fluids called completion fluids.
What is referred to as a workover operation relates to an operation performed in a producing or a potentially producing well. Workover fluids can be used in the producing well in circulation in a comparable way to drilling fluids or in the form of a spacer fluid.
During a well drilling operation, be it an oil well or not, a fluid is injected down to the drill bit through the drill pipes, the fluid flowing up to the surface in an ascending flow in the annular space defined by the hole drilled and the outside of the drill pipes. In order to perform rock drilling under good conditions, the fluid is determined in order to have particular properties.
Generally, the fluid must notably be capable of keeping the cuttings in suspension during periods of stopped circulation, of carrying along and driving effectively the cuttings towards the surface, of having a low filtration rate through the permeable hole walls, be sufficiently weighted to control the pressures, and less capable of cleaning the bit and the bit-gage surface.
Many additives for water-base fluids allowing the properties required for a good drilling fluid to be obtained are known.
In order to control the capacity of a fluid to prevent cuttings dispersion, a test referred to as a hot rolling cuttings test, which is for example described in document U.S. Pat. No. 4,664,818 or in document U.S. Pat. No. 5,260,269, is carried out.